Definition of Ankle

Ankle: The ankle joint is complex. It is made up of
two joints: the true ankle joint and the subtalar joint:

The true ankle joint is composed of 3 bones: the tibia
which forms the medial (inside) portion of the ankle; the fibula
which forms the lateral (outside) portion of the ankle; and the
talus underneath. The true ankle joint is responsible for the up-and-
down motion of the foot.

The subtalar joint is under the true ankle joint and
consists of the talus on top and calcaneus on the bottom. The
subtalar joint is responsible for the side-to-side motion of the
foot.

The ends of the bones in the joints of the ankle are covered by
cartilage. The major ligaments of the ankle are: the anterior
tibiofibular ligament (connecting the tibia to the fibula),
the lateral collateral ligaments (attaching the fibula to the
calcaneus to give the outside of the ankle stability), and the
deltoid ligaments on the inside of the ankle (connecting the
tibia to the talus and calcaneus and providing medial stability to
the ankle).

In medicine, the ankle is the meeting of the leg and the foot; it
is strictly the articulation of the tibia, fibula, and the talus. In
popular usage, the ankle is often taken to be the ankle joint proper
plus the surrounding region including the lower end of the leg and
the tarsus, the start of the flat of the foot.